In order to reduce air pollution, there is a modern trend toward electrically powered automobiles. These electrically powered automobiles have rechargeable batteries therein. The power of the batteries is used to propel the automobile and to provide for other power needs thereof. The design of such a vehicle is a careful balance between payload, performance, range between charging, acceleration, and speed. No matter what the combination of these criteria, there is need to recharge the batteries periodically so that the automobile may be taken on another excursion. With fairly large batteries, there is need to recharge a substantial amount of power. Since the recharging time when an automobile is unavailable should be minimized, high charging rates are desirable. If an ordinary plug is to be used, the plug must be suited for high power, which brings about a risk of harm to the operator and/or other people in the vicinity from contact with parts of the electrical supply system.
It is, thus, desirable to make a coupling between the charging station and the automobile which does not require the direct transfer of electricity. A magnetic coupling is desirable. In accordance with this invention, an inductive charge coupler can be manually handled and inserted in an appropriate inductive charge receptacle slot in the automobile. The inductive charge coupler is a transformer primary and contains an appropriate magnetic core. The inductive charge receptacle slot contains the transformer secondary winding(s) together with the rest of the magnetic core. The transformer secondary in the automobile is connected through appropriate electrical equipment to the battery for the charging thereof.
The frequency is preferably higher than the ordinary power line frequency, and high charge rates are above 10 kilowatts. The result is that the amount of heat dissipated from the transformer coils, magnetic coils and other electronics contained within the inductively coupled separable transformer can exceed 50 watts. It is desirable to cool the entire transformer and its associated electronics, such as rectifiers, so that internal temperatures do not exceed the critical operating range of the materials used in the transformer, rectifier junction or surface touch temperatures to maximize performance.
Cooling could be achieved by cooling devices in the automobile, but it is desirable to limit the total automobile weight as much as possible. It is, thus, desirable to improve the cooling methods for the inductive charge coupler. It is also useful to employ offboard cooling sources to efficiently cool the transformer secondary coil and the related magnetic core. The use of offboard cooling at the charging station permits cooling air to be provided through the inductive charge coupler connections and inductive charge coupler. When the inductive charge coupler is inserted into the onboard transformer secondary inductive charge receptacle, there is direct coupling with internal air flow passages in the transformer secondary and associated electronics such as rectifiers and capacitors associated wit the inductive charge receptacle. This arrangement couples large offboard cooling capacity with onboard transformer and electronics cooling, thereby vastly extending the cooling capacity. As a result, the charging transformer can be more compact, lighter, more efficient and more reliable. This offboard cooling reduces the temperature of the entire transformer and associated electronics and reduces the surface temperature of the removable primary inductive charge coupler.